It has become customary in the last several years to bury the cables of telephone systems approximately 12 to 30 inches below the earth's surface, depending on local soil conditions. At spaced points throughout the telephone system, in order to gain access to the wire or cable conductors, as for example, to provide service to customers, join lengths of wire or cable together, and permit other necessary functions, a loop of cable is brought above grade installed in a device generally referred to as a "buried plant terminal" or "buried plant housing."
In the housing the wire pairs within the cables are then made accessible for future working by removing the insulating jacket (S), metallic shields, or other wrappings surrounding the conductors. A necessary operation, when the metallic shields are stripped away from a portion of the cable length, is to reliably re-establish the electrical continuity of the shield, to provide continuous electrical protection by shielding the conductors from lightning surges which could cause dielectric failure of the conductors, and to shield the conductors from extraneous foreign voltages which may cause "noisy" circuit conditions. Electrical shield continuity at each buried plant housing or terminal is achieved by electrically interconnecting the shields on each side of the stripped area to a common point by bonding harnesses. It is in the establishment of such shield continuity that the present invention is particularly useful.
Bonding harnesses comprise mainly an electrically insulated conductor (either solid or stranded wire) attached at one end to the wire or cable shield and at the other end to a common connection point within the housing or terminal. It is important to note that the free end (the end opposite that which is attached to the shield) of each harness is attached to a common electrical bonding point to achieve interconnection of wire and cable shields. The bonding point may further be grounded in some cases.
According to existing industry standards, the common connection point or "connector " must be capable of accommodating eight bonding harness wires. One type of connector, illustrated in FIG. 2 of the drawings, includes a relatively flat plate member having a hole at one end for mounting the device to the terminal or housing wall, and a barrel member at the other end with an opening therethrough to receive the bared ends of bonding harnesses. The barrel is, in turn, provided with a tapped hole through a wall thereof which receives a slotted set screw. In practice, the bonding harness wires are grouped together and all placed within the opening in the barrel portion of the aforementioned connector. The set screw is tightened to apply sufficient mechanical pressure to achieve electrical interconnection and mechanical support for the bonding harnesses.
Such a device and method for interconnecting the cable shields within the terminal housing creates several undesirable situations. For example, in conducting routine testing or in trouble shooting, it is necessary for maintenance personnel to disconnect or electrically isolate the shield of a particular wire or cable. Isolation of a selected shield is achieved by removing the bonding harness wire associated with the selected wire or cable from the connector. However, it is easily seen that removal of one bonding harness wire from the barrel of the aforedescribed connecting device generally results in removal of other harness bonding wires. Further, where a multiplicity of wires and cables are looped through a given terminal or housing, confusion may arise as to which bonding harness wire is associated with which wire or cable. After the selected bonding harness has been removed, the remaining harnesses should be reassembled within the connecting device, so that the other, unselected harnesses will retain the shield continuity. Besides the consumption of time necessitated by the foregoing procedure, difficulty is frequently encountered in maintaining all bonding harness wires in proper position during retightening of the set screw and therefore the shield continuity may be disrupted. After the test is completed on the selected bonding harness, the set screw must again be loosened and the selected bonding harness returned into the opening, which sometimes causes further difficulty in repositioning all bonding harness wires properly for retightening of the set screw.
It has further been found that the reliability of the electrical connection is a direct function of the degree to which the set screw is tightened. While insufficient tightening of the set screw may result in undesirable loss of electrical interconnection of shields due to loosening effects from vibrations in the earth attributed to heavy roadside traffic, overtightening of the set screw may result in rupture of the bared ends, which could lead to unreliable electrical interconnection of the shield. Such loss or interruption of the shield continuity can result in derogatory effects on the performance of the cable, severe damage if struck by lightning, all of which may occasion high maintenance cost or replacement of complete sections of wire or cable between adjacent terminal or housing locations.